just to confirm, you cannot force power from rb5009UPr to a passive port right?

[Spirch]

when using the powerbrick provided which is 48v-2a from rb5009UPr setting forced poe out to rb951ui passive poe in (8-30v)

it will not work or break something right?

[mkx]

Apart from very few models (which use multiple power sources or have internal power adapter), all Mikrotiks pass voltage as is. So if you power your RB5009UPr with 48V adapter, all PoE out will have 48V. Connecting RB951, which requires 8-30V, will likely have bad consequences.
You have option to connect additional power source to RB5009UPr (e.g. 24V) and set PoE-out voltage to “low” … in that case your RB951 should be fine.

[Spirch]

Apart from very few models (which use multiple power sources or have internal power adapter), all Mikrotiks pass voltage as is. So if you power your RB5009UPr with 48V adapter, all PoE out will have 48V. Connecting RB951, which requires 8-30V, will likely have bad consequences.
You have option to connect additional power source to RB5009UPr (e.g. 24V) and set PoE-out voltage to “low” … in that case your RB951 should be fine.

that was my understanding, thanks